A phosphor is used in a ultraviolet and visible light excited light-emitting device, such as a white LED; an electron beam excited light-emitting device, such as a CRT; an ultraviolet light-emitting device, such as a three-wavelength fluorescent lamp; a vacuum ultraviolet excited light-emitting device, such as a plasma display panel (hereafter abbreviated as “PDP”), a rare-gas lamp; and so on.
For example, a white LED is composed of a combination of a light emitting device that emits blue light, and a phosphor that is excited by the blue light and emits yellow light (including yellowish green and orange colors); and emits white light as an entire white LED by mixing the blue light and the yellow light. Since the wavelength range of the light emitted from the light emitting device that emits blue light is between 350 and 500 nm, as a phosphor that is excited by the light within the wavelength range and emits yellow light, an yttrium-aluminum-garnet phosphor (Y3Al5O12:Ce), which as an oxide containing Y and Al has been heretofore used (for example, refer to Patent Document 1).
However, since the yellow light emitted from Y3Al5O12:Ce (peak wavelength: around 527 nm) has a small amount of red component (580 to 700 nm) and is strongly greenish, when combined with a blue LED, there has been a problem wherein white light cannot be obtained; and a phosphor that is excited by the light emitted from a blue LED, whose light emitting peak is 540 nm to 560 nm, which is a longer wavelength than conventional wavelength, and has more red components has been demanded.
Patent Document 1: JP-A-2003-8082